    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
     <html xmlns="http://www.w3.org/1999/xhtml">  
    <head>  
    <title>DIV CSS遮罩层</title>  
    <script language="javascript" type="text/javascript">  
    function showdiv() {              
                document.getElementById("bg").style.display ="block";  
                document.getElementById("show").style.display ="block";  
            }  
    function hidediv() {  
                document.getElementById("bg").style.display ='none';  
                document.getElementById("show").style.display ='none';  
            }  
    </script>  
    <style type="text/css">  
            #bg{ display: none;  position: absolute;  top: 0%;  left: 0%;  width: 100%;  height: 100%;  background-color: black;  z-index:1001;  -moz-opacity: 0.7;  opacity:.70;  filter: alpha(opacity=70);}  
            #show{display: none;  position: absolute;  top: 25%;  left: 22%;  width: 53%;  height: 49%;  padding: 8px;  border: 8px solid #E8E9F7;  background-color: white;  z-index:1002;  overflow: auto;}  
    </style>  
    </head>  
    <body>  
    <input id="btnshow" type="button" value="Show" onclick="showdiv();"/>  
    <div id="bg"></div>  
    <div id="show">测试  
    <input id="btnclose" type="button" value="Close" onclick="hidediv();"/>  
    </div>  
    </body>  
    </html>  